While DNA and RNA were already discovered around 1870, the crucial role of DNA in determining genetic inheritance was not demonstrated until 1943.
Once it became clear that genes are activated to make useful proteins, it became of the greatest interest to discover the molecular machinery involved. RNA was known to play some kind of role in protein synthesis. But it remained unclear how ribosomal RNA received specific information from DNA. Scientists acknowledged that there was a ‘missing link’, a ‘messenger’ that allows translation of the information embedded in DNA to proteins. They named this hypothetical molecule "messenger RNA" (mRNA). The actual existence of mRNA was confirmed by experiments in the early 1960ies.
Messenger RNA represents the template that copies the information contained in the DNA sequences. From the perspective of developing immunotherapies, it is interesting to note that mRNA can be used to deliver genetic information i.e. to stimulate dendritic cells but can also be used as vehicle to deliver tumor antigens to dendritic cells, which in their turn play another important role in initiating and promoting immune reactions.
Unlike DNA-based therapy, mRNA does not have the risk of integration into chromosomes. Upon therapeutic delivery, mRNA only results in transient translation of a specific protein and is completely degraded through physiologic pathways. It is in reality the expressed protein that will exert the desired physiological action. mRNA is therefore expected to be very well tolerated.